uid=HFR,o=lter,dc=ecoinformatics,dc=org
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public
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doi:10.6073/pasta/3df68d6d84a5fd5b357363ac706ba50f
Nonstructural Carbohydrates in Defoliated Oaks in Central Massachusetts 2019-2020
Audrey
Barker Plotkin
https://orcid.org/0000-0002-4473-9785
Meghan
Blumstein
https://orcid.org/0000-0003-0905-6265
Danelle
Laflower
Researcher
Greta
VanScoy
Researcher
2023
English
Carbon starvation posits that defoliation- and drought-induced mortality results from drawing down stored nonstructural carbohydrates (NSCs), but evidence is mixed and mortality is often observed prior to full drawdown of NSCs. We tested the relationship between defoliation severity, NSC drawdown, and tree mortality by measuring NSCs in mature oak trees defoliated by Lymantria dispar across a natural experimental gradient of defoliation severity. We collected stem and root samples from oaks (Quercus rubra and Q. alba) in interior forests (n=34) and forest edges (n=47) in central Massachusetts, USA. Total NSC (TNC; sugar + starch) stores were analyzed with respect to tree size, species, and defoliation severity, which ranged between 5 and 100%. Forest edge trees had higher TNC stores that were less sensitive to defoliation than interior forest trees. However, TNC stores declined significantly in both groups with increasingly severe defoliation. Furthermore, we observed a mortality threshold of 1.5% dry weight TNC. Our study draws a direct link between insect defoliation and TNC reserves and defines a TNC threshold below which mortality is highly likely. These findings advance understanding and improve model parametrization of tree response to insect outbreaks, an increasing threat with globalization and climate change.
carbohydrates
defoliation
disturbance
invasive species
mortality
oak
tree physiology
LTER controlled vocabulary
organic matter
disturbance
LTER core area
Harvard Forest
HFR
LTER
USA
HFR default
This dataset is released to the public under Creative Commons CC0 1.0 (No Rights Reserved). Please keep the dataset creators informed of any plans to use the dataset. Consultation with the original investigators is strongly encouraged. Publications and data products that make use of the dataset should include proper acknowledgement.
Creative Commons Zero v1.0 Universal
https://spdx.org/licenses/CC0-1.0.html
CC0-1.0
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf369
Central Massachusetts. Coordinates based on WGS84 datum.
-72.5308
-72.1676
+42.5313
+42.3144
60
300
meter
2018
2020
genus
Lymantria
species
dispar
genus
Quercus
species
alba
white oak
species
rubra
red oak
complete
Information Manager
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
hf-im@lists.fas.harvard.edu
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
(978) 724-3595
https://harvardforest.fas.harvard.edu
Study sites and sample selection
During the mid-late growing season of 2018, we established two study sites. We established plots in the Quabbin Watershed Forest (‘Forest’). Plots had varying defoliation severity, as classified by a published Landsat timeseries analysis (Pasquarella, V.J., Bradley, B.A, and Woodcock, C.E. 2017 Near-real-time monitoring of insect defoliation using Landsat time series. Forests 8(8), 275; doi:10.3390/f8080275.). Within plots, defoliation of oaks also varied. That is, even in lightly defoliated areas we observed a few oaks that were severely defoliated. We also tagged 85 individual oak trees from roadsides and hedgerows in and within 15 km of the mid-sized town of Amherst, Massachusetts (‘Town’). For each tree, we recorded diameter at breast height (DBH), species, and canopy position (1 = full sun; 2 = partially shaded; 3 = mostly/fully shaded). In the Forest plots, we recorded defoliation class (1 = 0-25% defoliated; 2 = 25-50% defoliated; 3 = 50-75% defoliated; 4 = 75-100% defoliated). For the Town trees, we estimated defoliation to the nearest 5%. These two sites were established independently and came together in Winter 2018-2019 for this study.
From these sites, we selected 34 Forest trees (from four plots) and 47 Town trees for NSC sampling, representing a range of defoliation severity in 2018. Note: we did not use the data collected from Quabbin Plot 6, because these trees likely died prior to autumn 2018, nor did we use the ‘Harvard Forest’ site in our analyses. All selected trees were alive in late summer 2018, although some were predicted to die within a year based on a visual assessment of crown dieback. Secondary selection criteria included sampling a range of tree size and species. Diameter of the sample trees ranged from 15-69 cm at the Forest site (mean 49 cm) and from 12-66 cm at the Town site (mean 35 cm). Most of the oaks at the two sites were red oak (Quercus rubra L., n = 66) but we included white oak (Q. alba L., n = 15) to the extent it was available.
NSC sampling
We sampled NSCs in February 2019, and again in February 2020. From each sample tree, we collected a 2 cm (under bark) sample of wood from: 1) the stem, at ~1.3 m height; and 2) a coarse root, at ~20 cm from the base of the tree. Samples were collected using a standard 4.3 mm diameter increment borer, stored on ice in the field, and then stored in a −80o C freezer until processing.
Tree defoliation, dieback, and mortality assessments
We assessed defoliation and/or dieback four times over the course of the study. At the initial defoliation assessment in late summer 2018, some of the Forest trees exhibited branch dieback and browning leaves. We recorded crown dieback and mortality status at leaf-out in May 2019, during June – August 2019 and in July – August 2020. A tree was presumed dead if it did not produce leaves; no tree that failed to leaf out in May 2019 produced leaves later that season or in 2020. Crown dieback was rated visually on a five-point scale (1 = 0-25 dieback; 2 = 25-50% dieback; 3 = 50-75% dieback; 4 = 75-99% dieback; 5 = dead). In 2019, we recorded defoliation by Lymantria dispar during their larval period from late May – early July. Despite high egg-mass counts in Fall 2018, high larval mortality in 2019 led to very low defoliation (Brown, 2019). There were few Lymantria dispar larvae and minimal defoliation in 2020.
NSC analysis
Total NSC reserves were extracted from freeze-dried and ground woody tissue samples following the protocol of Landhäusser et al. (Landhäusser SM, Chow PS, Dickman LT, Furze ME, Kuhlman I, Schmid S, Wiesenbauer J, Wild B, Gleixner G, Hartmann H, et al. 2018. Standardized protocols and procedures can precisely and accurately quantify non-structural carbohydrates. Tree physiology 38: 1764–1778.). In brief, after grinding the wood samples using a Wiley mill and then a ball grinder, we extracted sugars from 30 mg of dried tissue using 80% hot ethanol, then read them using a phenolic colorimetric assay and a spectrophotometer at 490 nm (ThermoFisher Scientific Genesys 180 UV-Vis Spectrophotometer). The methodology extracted and quantified all soluble sugars in the samples, including glucose, sucrose, fructose, and other oligosaccharides and glucans. We included two internal laboratory standards (Q. rubra stem-wood) with each set of samples, with sets within 10% of the laboratory estimate (42 mg g-1) accepted.
Starch was extracted from the tissue remaining after sugar extraction. We solubilized the tissue in NaOH, then incubated it with alpha-amylase and amyloglucosidase digestive enzymes, which digest starch into glucose. Solutions were assayed using a PGO-color reagent solution (Sigma Chemicals) and read on the spectrophotometer at 525 nm. Starch concentrations of mg glucose-starch-equivalent per g dry wood were calculated based on a glucose standard curve (Sigma Chemicals).
Harvard Forest Long-Term Ecological Research
Harvard Forest
324 North Main Street
Petersham
MA
01366
USA
(978) 724-3302
(978) 724-3595
https://harvardforest.fas.harvard.edu
https://ror.org/059cpzx98
pointOfContact
The Harvard Forest Long-Term Ecological Research (LTER) program examines ecological dynamics in the New England region resulting from natural disturbances, environmental change, and human impacts.
National Science Foundation LTER grants: DEB-8811764, DEB-9411975, DEB-0080592, DEB-0620443, DEB-1237491, DEB-1832210.
hf369-01-trees.csv
trees
hf369-01-trees.csv
9181
0ee2b78a27935483b7439c8f6510076f
1
\r\n
column
,
https://harvardforest.fas.harvard.edu/data/p36/hf369/hf369-01-trees.csv
site
site
Amherst
Town
Harvard Forest
Simes
Quabbin
Forest
NA
missing value
plot
plot name
plot name
NA
missing value
tree
tree number. Unique identifier is combination of plot and
tree
tree number
NA
missing value
tag
tag number for Quabbin plot trees that are part of related permanent plot
study
tag number for Quabbin plot trees
NA
missing value
point
one of 3 variable-radius plot centers established in 2018 in the Quabbin
plots
one of 3 variable-radius plot centers established in 2018 in the Quabbin
plots
NA
missing value
species
species
Q. alba
white oak
Q. rubra
northern red oak
NA
missing value
dbh.cm
diameter at breast height
centimeter
0.1
real
NA
missing value
can.exp
canopy exposure
1
full sun
2
partially shaded
3
mostly/fully shaded
NA
missing value
ref.class.18
defoliation class in 2018. Based on def.per.18 for the Amherst
trees
1
0-25% defoliated
2
25-50% defoliated
3
50-75% defoliated
4
75-100% defoliated
NA
missing value
def.per.18
percent defoliation in 2018; to nearest 5% for Amherst and mid-point of
ref.class.18 for Quabbin
dimensionless
0.1
real
NA
missing value
n.egg.masses.18
number of Lymantria dispar egg masses counted in summer-fall 2018; 30 means more
than 30 and 100 means WAY more than 30
number
1
whole
NA
missing value
cond.19
condition
D
dead
L
live in 2019
NA
missing value
defol.2019
defoliation class in 2019
1
0-25% defoliated
2
25-50% defoliated
5
dead
NA
missing value
dieback.2019
dieback classes
1
0-25% dieback
2
25-50% dieback
3
50-75% dieback
4
75-99% dieback
5
dead
NA
missing value
notes.18
notes about the tree in 2018
notes about the tree in 2018
NA
missing value
notes.19
notes about the tree in 2019
notes about the tree in 2019
NA
missing value
ind_leaf_defoliation_S19
average herbivory percent based on a sample of 30 individual leaves from
that tree; summer 2019; Amherst trees only
dimensionless
0.00000001
real
NA
missing value
defoliation_canopy_pct_F19
estimated percent defoliation; Amherst trees
dimensionless
0.1
real
NA
missing value
ind_leaf_defoliation_F19
average herbivory percent based on a sample of 30 individual leaves from
that tree; fall 2019; Amherst trees only
dimensionless
0.00000001
real
NA
missing value
new_eggmasses_below2m_19
number of new Lymantria dispar egg masses counted in fall 2019 below 2 m on the
tree
dimensionless
1
whole
NA
missing value
cond.20
condition in 2020
D
dead
L
live
NA
missing value
dieback.20
percent dieback in 2020
1
0-25% dieback
2
25-50% dieback
3
50-75% dieback
4
75-99% dieback
5
dead
NA
missing value
note.20
notes about the tree in 2020
notes about the tree in 2020
NA
missing value
94
hf369-02-nsc.csv
nonstructural carbohydrates
hf369-02-nsc.csv
35247
53564bf29ef81265aecde8100ebf205e
1
\r\n
column
,
https://harvardforest.fas.harvard.edu/data/p36/hf369/hf369-02-nsc.csv
vial.id
identifier for sample vial
identifier for sample vial
NA
missing value
site
site
Amherst
Town
Quabbin
Forest
Simes
Harvard Forest
NA
missing value
plot
plot name
plot name
NA
missing value
tree_id
unique identifier is combination of plot and tree
unique identifier is combination of plot and tree
NA
missing value
tissue
root or stem
root
root
stem
stem
NA
missing value
weight.mg
sample weight
milligram
0.01
real
NA
missing value
sugar.perc.dw
sugars in percent dry weight
dimensionless
0.000000001
real
NA
missing value
starch.perc.dw
starch in percent dry weight
dimensionless
0.000000001
real
NA
missing value
tnc.perc.dw
total nonstructural carbohydrates (sugars and starches) in percent dry
weight
dimensionless
0.000000001
real
NA
missing value
date
date that the sample was collected in the field
YYYY-MM-DD
1 day
NA
missing value
month
month that the sample was collected in the field
month that the sample was collected in the field
NA
missing value
year
year that the sample was collected in the field
YYYY
1 year
NA
missing value
note
note about the sample
note about the sample
NA
missing value
360
invasive
community
short-term measurement
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf344
https://harvardforest.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf424